Researchers have demonstrated a novel method for controlling magnetism using light, potentially paving the way for faster, more energy-efficient electronic devices. A team at the University of Basel and ETH Zurich successfully reversed the polarity of a specialized ferromagnetic material with a precisely tuned laser pulse and crucially, without the need for heating the material – a traditional requirement for altering magnetic orientation.
The breakthrough, , centers around a unique ferromagnet constructed from twisted atomic layers. Ferromagnets, like those found in compass needles and refrigerator magnets, rely on the alignment of countless electron spins, each generating a tiny magnetic field. When these spins align, the material exhibits a strong magnetic field. Traditionally, changing the direction of this field – flipping the polarity – requires heating the material above a critical temperature, allowing the spins to reorient before cooling down. This process is energy-intensive and relatively slow.
The team bypassed this thermal requirement by leveraging the properties of a topological material. Topology, refers to a state of matter that is remarkably resistant to change. The specific material used consists of twisted atomic layers, creating a robust structure that responds to external stimuli in a predictable way. By applying a short laser pulse, the researchers were able to induce a change in the alignment of the electron spins, effectively flipping the magnetic polarity.
“In a ferromagnet, combined forces are at work,” explains research published by the University of Basel. “In order for a compass needle to point north or a fridge magnet to stick to the fridge door, countless electron spins inside them, each of which only creates a tiny magnetic field, all need to line up in the same direction.” The new method circumvents the need to overcome the forces maintaining that alignment through heat.
The implications of this discovery are significant. Current electronic circuits rely on the flow of electrons to represent and process information. Controlling magnetism with light offers the potential to create entirely new types of circuits where information is encoded and manipulated using magnetic polarity, switched by light signals. Such “photomagnetic” circuits could be significantly faster and more energy-efficient than conventional electronic circuits.
The research team utilized a blue laser pulse to alter the ferromagnetic state within the material. Visualizations of the experiment show the laser interacting with the twisted atomic layers (represented in red), inducing the polarity change. The process is described as an inversion of the magnetic field direction, comparable to flipping a compass needle.
While the material used in the experiment is currently specialized, the researchers believe the underlying principles could be applied to a wider range of ferromagnetic materials. The ability to control magnetism with light opens up possibilities for creating adaptable electronic circuits – circuits that can be reconfigured on the fly to perform different functions. This adaptability could be particularly valuable in areas such as artificial intelligence, where algorithms and processing requirements are constantly evolving.
The key advantage of this technique lies in its speed and efficiency. Because the polarity change is induced by light rather than heat, it happens almost instantaneously. This eliminates the delays associated with heating and cooling cycles, potentially leading to dramatically faster processing speeds. The absence of heating reduces energy consumption, making the technology more environmentally friendly.
The research builds on existing understanding of ferromagnetism. For a material to become ferromagnetic, its temperature must be below a critical value, allowing the electron spins to align. Previous methods of altering polarity required exceeding this critical temperature, a process that is both time-consuming and energy-intensive. The new technique circumvents this limitation, offering a more direct and efficient approach.
The work, a collaboration between ETH Zurich and the University of Basel, was recently published in the scientific journal Nature. Researchers at both institutions contributed to the project, led by Prof. Dr. Tomasz Smoleński at the University of Basel and Prof. Dr. Ataç Imamoğlu at the ETH in Zurich.
The development represents a significant step forward in the field of spintronics, which explores the use of electron spin, rather than just electron charge, to store and process information. While still in its early stages, this research suggests a future where light-controlled magnetism could revolutionize the way we build and interact with electronic devices.
